docs: def do_layout(self, *args):
          """Put the bar where it's supposed to be, and size it in proportion to
          the size of the scrollable area.
  
          """
          if 'bar' not in self.ids:
              Clock.schedule_once(self.do_layout)
              return
          if self.orientation == 'horizontal':
              self.ids.bar.size_hint_x = self.hbar[1]
              self.ids.bar.pos_hint = {'x': self.hbar[0], 'y': 0}
          else:
              self.ids.bar.size_hint_y = self.vbar[1]
              self.ids.bar.pos_hint = {'x': 0, 'y': self.vbar[0]}
          super().do_layout(*args)